Pulse transformer fabrication



Jul 1, 1969 H. K. HAZEL 3,452,431

PULSE TRANSFORMER FABRICATION Filed Aug. 8, 1966 Sheet of 4 1 F i G q 16 i 10 I "i L is) 12 v INVENTOR HERBE RT K. HAZEL ATTORNEY y 1, 1969 H. K. HAZEL PULSE TRANSFORMER FABRICATION S eet Filed Aug. 8 1966 2 AU 70 7d y 1969 H. K. HAZEL PULSE TRANSFORMER FABRICATION Sheet 3 of 4 Filed Aug. 8, 1966 FIG. 7

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July 1, 1969 H. HAZEL 3,452,431 A PULSE TRANSFORMER FABRICATION Filed Aug. 8. 1966 Sheet 4 of 4 United States Patent US. Cl. 29-605 6 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a method of fabricating a winding on a core wherein a number of wires are bent around the core to form single turns of wire, then the wires are skewed relative to one another, and then the wires are welded together such that a multiturn winding is formed.

The present invention relates to the fabrication of windings on cores and more particularly to joining wire segments together on cores to form windings.

Usually the multi-turn windings of pulse transformers are wound on the cores of the transformers by wrapping continuous lengths of wire around the cores. One problem with this method is that the electrical characteristics of the pulse transformers so produced differ materially from one transformer to another. These material differences are due to a large degree on the inability to hold the interwire spacings and the core to wire spacings within desired tolerances with known wire wrapping techniques and to repeat the same spacings for transformer after transformer.

Therefore it is an object of the present invention to provide a new method of forming windings on cores.

Another object of this invention is to provide a method for fabricating cores which enables accurate spacing of the wires with respect to one another and with respect to the core body.

Other objects of this invention include providing an efiicient method of forming windings on cores and providing a rapid method of forming windings on cores.

In accordance with the present invention, a new method of winding cores is provided. This method involves the forming of separate segments of wires around the cores and then joining the ends of the various segments together to complete a winding of the core. By forming windings on the core in segments in this manner, it is possible to maintain interwire spacings and core to wire spacings within close tolerances and to very rapidly and eificiently fabricate windings on cores.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings, of which:

FIGURE 1 illustrates the threading of wires through a core;

FIGURE 2 illustrates the fixing of the position of the wires relative to the core by splined mandrels;

FIGURE 3 illustrates the shaping of the wires around the core;

FIGURE 4 shows the wires positioned around the core in U-shaped segments;

FIGURE 5 illustrates skewing the exterior portion of the wires relative to the core and the interior portions of the wire;

FIGURE 6 shows the wires on the core after they have been skewed in accordance with the operation illustrated in FIG. 5;

FIGURE 7 illustrates the cutting of the exterior legs of the wires after skewing;

FIGURE 8 illustrates the final forming of the interior legs of the wires;

FIGURE 9 illustrates the cutting of the interior legs of the wires;

FIGURES 10 and 11 illustrate the welding of the ends of the wires together to make complete windings; and

FIGURE 12 shows a top View of the core after its completion.

Referring now to FIG. 1, the core 10 to be wound is positioned over an opening on a supporting plate 12. Positioned beneath the plate are spools 14 of uninsulated wires 16 which are drawn up through the apertures in the core 10 and the plate 12 so that one wire 16 is positioned through the core 10 for each turn of the windings on the core. FIG. 1 is a schematic in which a number of spools 14 and wires 16 have been left out for purposes of clarity, However, if there were to be two windings of 20 turns each, there would be 40 spools 14 to thread 40 wires 16 through the plate in the described manner. Preferably the core 10 is made of insulating material to prevent the shorting out of the windings of the uninsulated wires 16. However a conductive core can be employed if it is given an insulating coating prior to the threading of the wires 16 through the core as described above.

After the wires 16 have been threaded through the core, the wires are oriented against the interior of the core 10 as illustrated in FIG. 2. First, a splined mandrel 18 with protruding tip 20 is passed upward through the aperture in the core 10. This fixes the wires against the interior of the core 10 in the grooves 22 of the mandrel 18 so that they are equally spaced around the interior of the core 10. Thereafter a second splined mandrel 24 with a socket 26 is mated with the first splined mandrel 18. Once the protruding tip 20 and the socket 26 have been mated, the core is transferred from the first splined mandrel 18 to the second splined mandrel 24 and there positioned against a shoulder 28. Then, the wires 16 are out from the spools 14, and the second splined mandrel 24 with the core 10 positioned on the shoulder 28 is moved to a new fixture for further fabrication.

In this new fixture, force F is exerted on the top of the core 10 to hold the Wires 16 between the grooves and the interior wall of the core 10 and between the shoulder 28 and the bottom of the core 10, as illustrated in FIG. 3. While the core is so held, sliding members 30 move radially inward towards the core 10 and in so doing capture the exterior portion of the wires 16 in a groove 32 in their leading edge thereby bending the wires upwardly around the exterior wall of the core 10. With all the interiorly moving members 30 positioned against the core 10 in this manner the wires 16 form U-shaped segments around the core, as illustrated in FIG. 4.

In the next step of fabrication the wires are skewed as shown in FIG. 5. As illustrated, the sliding members 30 hold the exterior portions of the wires 16 stationary against the exterior wall of the core 10 while the mandrel 24 with the core 10 on it is rotated with respect to the inwardly moving members 30. This causes the core 10 and the interior portions of the wires 16 to move relative to the exterior portions of the wire 16 causing a skewing of the wires 16 as illustrated in FIG. 6. As shown, each of the interior portions of the wire have been skewed two wire positions by the rotation of the mandrel 24. This is because two windings are to be fabricated on the core 10. A different number of windings can also be fabricated by this method by merely changing the amount of the skew; for instance, if a single winding is wanted, the wires 16 are skewed only one wire position, and if three windings are wanted, the wires are skewed three wire positions and so on.

With the skewing complete, the exterior portions of the wires 16 are cut off flush with the top of the core as illustrated in FIG. 7. Then the interior portions of wires 16 are bent down and folded over the top of the core 50 that the interior segment of wire extends radially out from its position against the interior of the core 10. So bent, the interior portion of each wire passes over the cut exterior portion of a wire displaced by two positions from it as shown in FIG. 8.

As illustrated in FIG. 9, each interior portion is then clipped slightly beyond the edge 38 of the interiorly moving members 30 by a downwardly moving blade 40. When this cutting operation is complete, all the wires extend approximately the same distance beyond the outer edge of the core 10. The wires are then ready for connection together. This is done by welding. As illustrated in FIGS. and 11, a welding tip 42 is positioned close to each extending end of wire 16 and an arc is drawn by making the welding tip 42 negative with respect to the wire 16. This causes the wire to melt joining the two overlapping ends together and positioning them closely to the edge of the core 10 as illustrated in FIG. 11. When the ends melt together the arcing stops because the space between the different potentials is too large to be bridged by the arc. With the completion of the welding, the windings are fin: ished and the core 10 with the windings on it is coated with an insulating substance. To provide leads 44 for windings, one set of opposing ends of wires 16 for each winding are not cut and welded together as shown in FIGS. 7 through 11. Instead they are left long and wardiy as shown in FIG. 12.

The invention has been disclosed abovein connection with the manufacture of pulse transformers. Of course other types of transformers and other wound electrical devices may be wound using the teachings of this invention.

Therefore, while the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

What is claimed is: 1. A method of fabricating a winding on a core comprising the steps of dressed outan electrode and certain of the ends of the turns of wire so that each of those certain ends melts and flows together with the end of the wire with which it is aligned by the skewing of the ends.

3. A method of fabricating windings on a toroidal core comprising the steps of:

(a) bending a number of flexible wires around the core to form on the core separate U-shaped segments of wire;

(b) skewing the arms of the U-shaped segments wire relative to one another so that each arm of each U- shaped segment is positioned on a common radius of the core with the arm of another U-shaped segment;

(c) bringing together the ends of radially opposed arms; and

(d) welding together the arms that have been brought together to thereby form windings with the U-shaped segments.

4. Themethod of claim 3 wherein the skewing of the arms is sufficient to position on a common radius arms of two U-shaped segments separated by at least one other U-shaped segment.

5. The method of claim 4 wherein the bringing together of the radially opposed arm comprises bending the arm positioned along the interior to the cores outwardly along the radius common to both arms so that it extends past the other of the radially opposed arms.

6. The method of claim 5 wherein said welding comprises drawing an are between an electrode and the ends of the arms bent in bringing the radially opposed arms together so as to melt said ends and causes each of them to flow together with the arm positioned with it on a common radius of the core.

(a) bending a number of flexible wires around the core to form on the core separate single turns of wire;

(b) simultaneously skewing the ends of all turns of wire relative to one another to align each end of the turns with the end of another turn; and

(c) welding the turns of wire together to form a multiturn winding.

2. The method of claim 1 wherein the welding of the turns of wire includes the steps of drawing an are between References Cited UNITED STATES PATENTS 1,801,214 4/1931 Von Henke 29-605 X 1,852,805 4/1932 Frank 2960S X 2,479,987 '8/ 1949 Williams 29475 X 3,181,803 5/1965 Warburton et al. 2424 3,243,750 3/1966 Collins 29-605 X 3,286,327 11/1966 Ganci 29-618 JOHN F. CAMPBELL, Primary Examiner.

C. E. HALL, Assistant Examiner.

U.S. Cl. X.R. 

